DirectionsBrush the madeleine molds with the softened butter; dust with flour. Combine the sugar and eggs in a bowl and beat with a whisk or an electric beater until pale yellow and creamy. Add the zest, flour, baking powder, and vanilla and beat until blended. Beat in the softened butter and then the milk. Set aside for 15 mn. Preheat the oven to 400ºF. Fit a pastry bag with the medium plain tip and fill with the batter. Pipe the batter into the molds, filling each indentation to the rim. Bake until golden, 12 to 15 mn. Unmold the madeleines immediately onto a cake rack and let cool completely. Store in an airtight container.